Re: [PATCH 2/2] iio: adc: ti_am335x_adc: make sample delay, open delay, averaging DT parameters

[Vignesh R <vigneshr@ti.com>]

On Thursday 09 April 2015 07:49 PM, Jonathan Cameron wrote:
> On 31/03/15 12:12, Vignesh R wrote:
>> Add optional DT properties to set open delay, sample delay and number
>> of averages per sample for each adc step. Open delay, sample delay
>> and averaging are some of the parameters that affect the sampling rate
>> and accuracy of the sample. Making these parameters configurable via
>> DT will help in balancing speed vs accuracy.
>>
>> Signed-off-by: Vignesh R <vigneshr@ti.com>
> All looks fine to me, but I would ideally like a devicetree
> ack on this one.
> 
> Jonathan

Gentle ping...

Regards
Vignesh
>> ---
>>  .../bindings/input/touchscreen/ti-tsc-adc.txt      | 24 ++++++++++
>>  drivers/iio/adc/ti_am335x_adc.c                    | 54 +++++++++++++++++++---
>>  2 files changed, 72 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>> index 6c4fb34823d3..8aafbe87f0eb 100644
>> --- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>> +++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>> @@ -42,6 +42,27 @@ Optional properties:
>>  			 hardware knob for adjusting the amount of "settling
>>  			 time".
>>  
>> +- child "adc"
>> +	ti,chan-step-opendelay: List of open delays for each channel of
>> +				ADC in the order of ti,adc-channels. The
>> +				value corresponds to the number of ADC
>> +				clock cycles to wait after applying the
>> +				step configuration registers and before
>> +				sending the start of ADC conversion.
>> +				Maximum value is 0x3FFFF.
>> +       ti,chan-step-sampledelay: List of sample delays for each channel
>> +				  of ADC in the order of ti,adc-channels.
>> +				  The value corresponds to the number of
>> +				  ADC clock cycles to sample (to hold
>> +				  start of conversion high).
>> +				  Maximum value is 0xFF.
>> +       ti,chan-step-avg: Number of averages to be performed for each
>> +			  channel of ADC. If average is 16 then input
>> +			  is sampled 16 times and averaged to get more
>> +			  accurate value. This increases the time taken
>> +			  by ADC to generate a sample. Valid range is 0
>> +			  average to 16 averages. Maximum value is 16.
>> +
>>  Example:
>>  	tscadc: tscadc@44e0d000 {
>>  		compatible = "ti,am3359-tscadc";
>> @@ -55,5 +76,8 @@ Example:
>>  
>>  		adc {
>>  			ti,adc-channels = <4 5 6 7>;
>> +			ti,chan-step-opendelay = <0x098 0x3ffff 0x098 0x0>;
>> +			ti,chan-step-sampledelay = <0xff 0x0 0xf 0x0>;
>> +			ti,chan-step-avg = <16 2 4 8>;
>>  		};
>>  	}
>> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
>> index 2f818405ffbe..5ee597b4a1af 100644
>> --- a/drivers/iio/adc/ti_am335x_adc.c
>> +++ b/drivers/iio/adc/ti_am335x_adc.c
>> @@ -37,6 +37,7 @@ struct tiadc_device {
>>  	u8 channel_step[8];
>>  	int buffer_en_ch_steps;
>>  	u16 data[8];
>> +	u32 open_delay[8], sample_delay[8], step_avg[8];
>>  };
>>  
>>  static unsigned int tiadc_readl(struct tiadc_device *adc, unsigned int reg)
>> @@ -85,6 +86,7 @@ static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan)
>>  static void tiadc_step_config(struct iio_dev *indio_dev)
>>  {
>>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
>> +	struct device *dev = adc_dev->mfd_tscadc->dev;
>>  	unsigned int stepconfig;
>>  	int i, steps = 0;
>>  
>> @@ -98,20 +100,47 @@ static void tiadc_step_config(struct iio_dev *indio_dev)
>>  	 * needs to be given to ADC to digitalize data.
>>  	 */
>>  
>> -	if (iio_buffer_enabled(indio_dev))
>> -		stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1
>> -					| STEPCONFIG_MODE_SWCNT;
>> -	else
>> -		stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1;
>>  
>>  	for (i = 0; i < adc_dev->channels; i++) {
>>  		int chan;
>>  
>>  		chan = adc_dev->channel_line[i];
>> +
>> +		if (adc_dev->step_avg[i] > STEPCONFIG_AVG_16) {
>> +			dev_warn(dev, "chan %d step_avg truncating to %d\n",
>> +				 chan, STEPCONFIG_AVG_16);
>> +			adc_dev->step_avg[i] = STEPCONFIG_AVG_16;
>> +		}
>> +
>> +		if (adc_dev->step_avg[i])
>> +			stepconfig =
>> +			STEPCONFIG_AVG(ffs(adc_dev->step_avg[i]) - 1) |
>> +			STEPCONFIG_FIFO1;
>> +		else
>> +			stepconfig = STEPCONFIG_FIFO1;
>> +
>> +		if (iio_buffer_enabled(indio_dev))
>> +			stepconfig |= STEPCONFIG_MODE_SWCNT;
>> +
>>  		tiadc_writel(adc_dev, REG_STEPCONFIG(steps),
>>  				stepconfig | STEPCONFIG_INP(chan));
>> +
>> +		if (adc_dev->open_delay[i] > STEPDELAY_OPEN_MASK)alue corresponds to the number of ADC
>> +				clock cycles to wait after applying the
>> +				step configuration registers and before
>> +				sending the start of ADC conversion.
>> +				Maximum value is 0x3FFFF.
>> +       ti,chan-step-sampledelay: List of sample delays for each channel
>> +				  of ADC in the order of ti,adc-channels.
>> +				  The value corresponds to the number of
>> +				  ADC clock cycles to sample (to hold
>> +				  start of conversion high).
>> +				  Maximum value is 0xFF.
>> +       ti,chan-step-avg: Number of averages to be performed for each
>> +			  channel of ADC. If average is 16 then input
>> +			  is sampled 16 times and averaged to get more
>> +			  accurate value. This increases the time taken
>> +			  by ADC to generate a sample. Valid range is 0
>> +			  average to 16 averages. Maximum value is 16. {
>> +			dev_warn(dev, "chan %d open delay truncating to 0x3FFFF\n",
>> +				 chan);
>> +			adc_dev->open_delay[i] = STEPDELAY_OPEN_MASK;
>> +		}
>> +
>> +		if (adc_dev->sample_delay[i] > 0xFF) {
>> +			dev_warn(dev, "chan %d sample delay truncating to 0xFF\n",
>> +				 chan);
>> +			adc_dev->sample_delay[i] = 0xFF;
>> +		}
>> +
>>  		tiadc_writel(adc_dev, REG_STEPDELAY(steps),
>> -				STEPCONFIG_OPENDLY);
>> +				STEPDELAY_OPEN(adc_dev->open_delay[i]) |
>> +				STEPDELAY_SAMPLE(adc_dev->sample_delay[i]));
>> +
>>  		adc_dev->channel_step[i] = steps;
>>  		steps++;
>>  	}
>> @@ -407,9 +436,22 @@ static int tiadc_parse_dt(struct platform_device *pdev,
>>  
>>  	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {
>>  		adc_dev->channel_line[channels] = val;
>> +
>> +		/* Set Default values for optional DT parameters */
>> +		adc_dev->open_delay[channels] = STEPCONFIG_OPENDLY;
>> +		adc_dev->sample_delay[channels] = STEPCONFIG_SAMPLEDLY;
>> +		adc_dev->step_avg[channels] = 16;
>> +
>>  		channels++;
>>  	}
>>  
>> +	of_property_read_u32_array(node, "ti,chan-step-avg",
>> +				   adc_dev->step_avg, channels);
>> +	of_property_read_u32_array(node, "ti,chan-step-opendelay",
>> +				   adc_dev->open_delay, channels);
>> +	of_property_read_u32_array(node, "ti,chan-step-sampledelay",
>> +				   adc_dev->sample_delay, channels);
>> +
>>  	adc_dev->channels = channels;
>>  	return 0;
>>  }
>>
>